Ultra high frequency electronic device



Oct. 14, 1947.

v A. E. BOWEN ULTRA-HIGH-FREQUENCY ELECTRONIC bEvIcE Original Filed July 3, 1942 m WP... I. W

ATTORAEV Patented Oct. 14, 1947 VICE -Ari1'old :E. Bowen, Red Bank, N. 3., assignor to Bell llelep honeLaboratories,Incorporated, New York, 'N. 'Y., a corporation of New York Original application July 8, 1942, Serial No. 449.581. Divided and this application October 9., 1945., Serial .No. 621,365

This invention relates to systems employing resonators and resonant cavities so shaped and constructed as to be suitable for reaction with an electron stream to enablean electromagnetic field which may be set up in the resonator or resonant cavity to induce a variation in some characteristic property of the electron stream, or, to permit an interchange of energy between the resonator and the electron stream.

In particular the resonator may be in the shape of a short section of an elliptical cylinder, hollow inside and closed off by parallel plane sheets. A wave guide may be connected tothe resonator at a focal point or elsewhere according to the amount of impedance to be provided at the junction point.

The invention is applicable generally to amplifiers, oscillators, modulators, detectors and the like, particularly at ultra-high frequencies,

wherever it is desired toeffect direct interaction between an electromagnetic field and an electron stream.

This application is a division of my copending application Serial No. 449,581, filed July 3, 1942, which latter application is a continuation in part of my copending application Serial No. 387,432, filed April 8, 1941, Patent No. 2,408,409, issued October 1,1946,

The present application is specific to a combination of two elliptical cavity resonators with electronic coupling between one pair of respective focal points in the resonators and with a twodirectional coupling means connected between another pair of corresponding points in the two resonators, not necessarily focal points.

The invention is described with reference to an illustrative example, while its scope is indicated by the appended claims.

In the drawing:

Figs. 1 and 2 show a sectional view and a plan or elevational view, respectively, of an oscillator employing elliptical resonators and a stream of electrons.

In Figs. 1 and 2 there are shown two substantially elliptical resonators 31 and 38 with focal points indicated at 39 and 40. The resonators may be built with walls of copper or other suitable material, the inner surfaces, at least, being preferably highly conductive. Each resonator may be viewed as comprising a short section of elliptical cylinder closed off by parallel, plane end walls. Apertures are cut through the plane walls of each ellipse at focus 39 and the resonators are joined by a cylindrical conductive tube 4| covering the apertures. Additional apertures are 3 Claims. (Cl. 315 -39 out through the resonator Walls preferably near the periphery at a point remote from focus 39 and the resonators are joined at this point by a cylindrical conductive tube 42. Coax'ia'lly with the tube 42 .is placed a rod of conductive material 43 which is held in place by insulating hermetic .seals at 44 and 45. A hollow conductive cylinder '6 is fastened over an aperture '5 in the left-hand end wall of the resonator 3! as viewed in Fig. 1. The tube 6 is joined by means of a suitable hermetic seal 1 to an insulating envelope 8 of glass or other suitable material. Within the envelope 8 are provided the usual elements of an electron gun or beam projector 46 of any suitable type comprising, for example, a cathode 9, and an accelerating electrode ll! cooperating with the cylinder 6 .to direct an electron beam through the apertures in the resonators .3? and 38 aligned with the axis of tube 4!. A pair of gaps 41 and 4-8 is constituted, as indicated, in the path of the beam. The gap 48 is defined by the edges of the aperture 5 and the edges of an aperture in the right-hand end wall of the resonator 3'? at the entrance to the tube 4!. The gap 4'! is defined by the edges of an aperture in the left-hand end wall of the resonator 33 and the right-hand end wall of that resonator. Batteries ll, l2 and E3 or other suitable sources may be provided, respectively, for heating the cathode 9, energizing the accelerating electrode Ill and applying an acceler ating potential to the conductive system comprising resonators 31 and 38, and the tubes 4t, 42 and '6. The tube 4| serves not only as a passage for the electron stream but also as an electromagnetic shield defining a drift space Within which the electron 'bunching action hereinafter described may be effectuated free from fluctuating electromagnetic fields.

In the operation of the arrangement of Figs. 1 and 2, the electrons comprising the electron stream from the gun 46 are subjected to the gap 48 to interaction with any electromagnetic field which may exist in the resonator 3? and at the gap 4! with any such field that may exist in the resonator 38. An accidental irregularity in the charge density of the electron stream will suffice to set up an electromagnetic wave in the resonator 38 as the irregularity passes across the gap 41. The wave thus set up spreads through the cavity of the resonator 38 and converges again at the focus 40, inducing current in the conductor 43 where the latter crosses the resonator. An induced wave travels over the coaxial transmission line comprising the tube 42 and the conductor 43 into the resonator 31. A wave is induced in the latter resonator which wave in the course of propagation converges upon the gap 48. Each electron in its passage across the gap 48 either takes energy from or gives energy. to the electromagneticfield in the resonator 31, depending upon the phase of the field during its transit of the gap. The velocities of the electrons are varied v I in accordance with this energy interchange.

After leaving the gap 48, the velocity-varied electrons pass through the tube M where a group-- ing or bunching effect takes place, these electrons which have lost energy and have, as' a conseother electrons which entering later, have gained energy and have speeded up. Consequently, at a point some distance to the right of the gap 48,

the electrons are traveling in more or less well-J defined groups. Upon reaching the gap 41 the bunches of electrons may, if the length of the tube 4| and the initial speedof the electrons have been adjusted correctly, cross the gap 41 in opposition to the high frequency electromagnetic field,

thus contributing energy to the field, and in greater amounts than are absorbed by the thinly distributed electrons which may cross the gap '41 during the unfavorable phase of the high frequency field. The net energy contributed by the electron stream to the field tends to sustain and build up the original wave and thus to maintain the system in oscillation.

' It may be further noted that the wave above described, upon first arriving at the gap 48 and there initiating an electron group in the electron stream, is, in effect, reflected back through the resonator 31 and coaxial line 42, 43 into the resonator 38 and to gap 41. If the velocityof the electrons in the beam is'adjusted so that the electron bunch reaches the gap 41 at thesame time the reflected wave arrives there, or an integral number of cycles later, a fresh supply of energy is given to the wave and the oscillation is maintained. The adjustment in this case will quence, been slowed down being overtaken by.

4 I V collected at the right-hand end wall of the resonator 38 and returned to the battery l3.

The construction shown in Fig. 1 will be observed to require a minimum of insulating material and practically none in the space containing the high'freq'uency field.

What is claimed is:

g 1. An electronic oscillator comprising a pair of spaced elliptical cylindrical resonators, means in a path interlinking said resonators for producing an electron stream, said path forming asubstantially unidirectional coupling between said resonators'and passing substantially through a pair of focal points of said respective resonators, and

also satisfy the condition for oscillation specia coaxial transmission line forming a feedback path between another pair of points in said re-' spective resonators.

2. An electronic oscillator comprising a pair of spaced elliptical cylindrical resonators, means in a path interlinking said resonators for producing an electron stream, said path forming a substantially unidirectional coupling between said resonators and passing substantially through a pair of focal points of said respective resonators, and coupling means forming a feedback path between another pair of points in said respective resonators. V V

3. An oscillator comprising two flat, hollow elliptical resonators in each of which the foci are substantially the same distance apart, said resonators being placed with their fiat faces substantially parallel, first and second tubular members V separating said resonators and interconnecting the interior spaces thereof, the first of said tubular members connecting'a pair of respective foci and the second of said tubular members 1 having a conductive inner surface, a central conductor withinsaid second tubular member form ing with said member a concentric conductor transmission linetand means in a path interlinking said'rescnators and the first of said tubular members to project an electron beam through one of said resonators and through the first of said tubular members into the other of said resonators.

I v ARNOLD E. BOWEN.

REFERENCES CITED The following referencesare ofxrecordin'the file of this patent: I

UNITED STATES PATENTS' Number 'Name Date 2,381,320 Tawney Aug..7, 1945 2,318,106 Ryan May' l, 1943 

